Investigation of the potential usage of the powder product by drying olive pomace in functional food production

In this study, the potential of pomace, one of the olive by-products, as a suitable food ingredient in terms of composition and functionality by drying at different temperatures was investigated and its use as a real food matrix as pomace powder additive in cookies was evaluated. Fresh olive pomace was dried in a tray dryer at different temperatures (60, 70, and 80°C), and moisture and dry matter determinations were made throughout the process to calculate the drying kinetics. Nutritional composition, bioactive content, and functional properties of the dried olive pomace powders were determined. The ash, fat, pH, and nutritional value in the fresh olive pomace showed significant increases after the drying process, while moisture, water activity and soluble dry matter decreased. Additionally, it was observed that drying at different temperatures had no significant effect on the analyzed moisture content, fat content, bioactive content, color values (L*, a*, and b*), or techno-functional properties (p>0.05). The total phenolic content, total flavonoid content, and antiradical activity per gram of dry matter were 9.78±1.01 mg cafeic acid equivalent (CAE), 7.22±0.66 mg catechin equivalent (CE), and 60.21±8.74 µmol trolox equivalent (TE) for fresh olive pomace, respectively, while they varied between 4.39-4.68 mg CAE, 5.23-5.30 mg CE, and 38.17-39.02 µmol TE in the dried olive pomace powders. The olive pomace powders dried at 80°C, which showed the least loss of bioactive compounds and the quickest moisture removal, were preferred for use in cookies. Cookies were prepared by adding dried olive pomace powders at different ratios (1%, 2%, and 3%) to the cookie dough. The moisture, ash, protein, fat content, nutritional value, baking loss, rising ratio, color, sensory and textural properties, and bioactive properties (total phenolic content, total flavonoid content, and antioxidant activities) of the baked cookies were determined. Cookies enriched with olive pomace powder (1%, 2%, and 3%) had higher L* (darker) and a* values (redder) and lower b* values (less yellow) compared to the control cookies. A statistically significant increase in these values was observed as the concentration of added olive pomace powder increased (p<0.05). The addition of olive pomace powder increased the bioactive compound content of the cookies. According to the results obtained, the cookie containing 1% olive pomace powder was the most preferred in sensory evaluations. KEYWORDS: Olive Pomace, Bioactive Ingredients, Functional Food, Waste Recycling, Cookie